[patch 5/5] lightweight robust futexes: x86_64

[Ingo Molnar <mingo@elte.hu>]

x86_64: add the futex_atomic_cmpxchg_inuser() assembly implementation, and
wire up the new syscalls.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Acked-by: Ulrich Drepper <drepper@redhat.com>

----

 arch/x86_64/ia32/ia32entry.S |    2 ++
 include/asm-x86_64/futex.h   |   21 +++++++++++++++++++--
 include/asm-x86_64/unistd.h  |    6 +++++-
 3 files changed, 26 insertions(+), 3 deletions(-)

Index: linux-robust-list.q/arch/x86_64/ia32/ia32entry.S
===================================================================
--- linux-robust-list.q.orig/arch/x86_64/ia32/ia32entry.S
+++ linux-robust-list.q/arch/x86_64/ia32/ia32entry.S
@@ -688,6 +688,8 @@ ia32_sys_call_table:
 	.quad sys_ni_syscall		/* pselect6 for now */
 	.quad sys_ni_syscall		/* ppoll for now */
 	.quad sys_unshare		/* 310 */
+	.quad compat_sys_set_robust_list
+	.quad compat_sys_get_robust_list
 ia32_syscall_end:		
 	.rept IA32_NR_syscalls-(ia32_syscall_end-ia32_sys_call_table)/8
 		.quad ni_syscall
Index: linux-robust-list.q/include/asm-x86_64/futex.h
===================================================================
--- linux-robust-list.q.orig/include/asm-x86_64/futex.h
+++ linux-robust-list.q/include/asm-x86_64/futex.h
@@ -97,8 +97,25 @@ futex_atomic_op_inuser (int encoded_op, 
 static inline int
 futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
 {
-	return -ENOSYS;
-}
+	__asm__ __volatile__(
+		"1:	" LOCK_PREFIX "cmpxchgl %1, %2		\n"
+
+		"2:	.section .fixup, \"ax\"			\n"
+		"3:	mov	%3, %0				\n"
+		"	jmp	2b				\n"
+		"	.previous				\n"
+
+		"	.section __ex_table, \"a\"		\n"
+		"	.align	8				\n"
+		"	.quad	1b,3b				\n"
+		"	.previous				\n"
 
+	     : "=&a" (oldval), "=&r" (newval), "=m" (*uaddr)
+	     : "i" (-EFAULT)
+	     : "memory"
+	);
+
+	return oldval;
+}
 #endif
 #endif
Index: linux-robust-list.q/include/asm-x86_64/unistd.h
===================================================================
--- linux-robust-list.q.orig/include/asm-x86_64/unistd.h
+++ linux-robust-list.q/include/asm-x86_64/unistd.h
@@ -605,8 +605,12 @@ __SYSCALL(__NR_pselect6, sys_ni_syscall)
 __SYSCALL(__NR_ppoll,	sys_ni_syscall)		/* for now */
 #define __NR_unshare		272
 __SYSCALL(__NR_unshare,	sys_unshare)
+#define __NR_set_robust_list	273
+__SYSCALL(__NR_set_robust_list, sys_set_robust_list)
+#define __NR_get_robust_list	274
+__SYSCALL(__NR_get_robust_list, sys_get_robust_list)
 
-#define __NR_syscall_max __NR_unshare
+#define __NR_syscall_max __NR_get_robust_list
 
 #ifndef __NO_STUBS